1. Field of the Invention
The invention relates to a method for producing aminoorganosilanes by reacting an amine with (haloorganyl)silanes.
2. Description of the Related Art
The prior art discloses various methods for producing aminoorganosilanes. The production of amino functional organosilanes is effected predominantly by reacting chlorofunctional organosilanes with very different types of organic amines or ammonia. As a rule, the procedure is such that at least two moles of amine or ammonia are used per mole of chlorofunctional organosilane, so that, in addition to the formation of the aminofunctional organosilane, there is still sufficient amine component available for converting the liberated hydrogen chloride into the corresponding amine hydrochloride or ammonium chloride.
In particular, the high availability of (chloroalkyl)silanes is advantageous. These silanes are obtainable by photochlorination of alkylsilanes or hydrosilylation of halogen-substituted olefins onto Si—H-containing compounds, and are used, for example, as intermediates for the synthesis of a multiplicity of organofunctional silanes. Furthermore, it is possible in this method to rely not only on ammonia but also on a large number of readily available primary and secondary amines for synthesizing the (N-organylaminoorganyl)- and (N,N-diorganylaminoorganyl)triorganylsilanes, which permits a very wide range of use of the method and thereby economical product change in existing industrial manufacturing plants.
GB 686,068 A discloses (amino)-, (N-organylamino)- and (N,N-diorganylaminomethyl)- or (N,N-diorganylaminoethyl)triorganylsilanes. Furthermore, GB 686,068 A describes a method for reacting corresponding (chloromethyl)- or (bromomethyl)triorganosilanes with ammonia, a primary or secondary amine at temperatures of at least 50° C. for the production of the (aminoorganyl)-, (N-organylaminoorganyl)- and (N,N-diorganylaminoorganyl)triorganylsilanes. As a rule, the (chloromethyl)- or (bromomethyl)triorganosilanes are initially introduced into a flask or autoclave, depending on the boiling points of the amine compounds used, and are heated to temperatures above 100° C., preferably 110-130° C. In the case of higher-boiling amines (e.g. cyclohexylamine), the sequence of mixing can be reversed, i.e. the (chloromethyl)- or (bromomethyl)triorganosilanes are added to the heated amine.
According to a method described in DE 1812564 A1, (aminomethyl)silane derivatives are produced by reacting a (chloromethyl)- or (bromomethyl)silane derivative with ammonia or a primary amine. The reaction is effected at temperatures of 80 or 100° C. in a period of 3 or 2 hours, the amine having been initially completely introduced in a molar excess of 1:3.2-6 as early as the beginning of the reaction.
DE 10 2004 060 627 A describes a variation of these methods in which the abovementioned reactions are carried out continuously.
The prior art further discloses methods for reducing halide contents in alkoxysilanes. For example, EP 0702017 A discloses methods based on precipitation of dissolved amine hydrochloride moieties by addition of alkali metal or alkaline earth metal alcoholate salts. An alternative method which is said to permit reduction of chloride content in alkoxysilanes by introduction of ammonia is described in DE 19941283 A1.
A disadvantage of all these methods is the fact that ammonium halides, optionally organically substituted, are formed in quantitative amounts as byproducts and have to be separated off as solids. Separating off such large amounts of solid is time-consuming and hence expensive and moreover requires production plants which have appropriate separation devices, for example powerful and therefore expensive centrifuges. However, this is not the case in many plants—in particular in most multipurpose plants as are typically used for producing fine chemicals.
Here, for example, U.S. Pat. No. 6,452,033 A describes the production of aminoethylaminoorganyltriorganylsilanes by reacting the corresponding chlorofunctional organosilanes with ethylenediamine, the above-mentioned phase separation for separating the hydrochlorides being used in various ways. However, a disadvantage of this method is the fact that it is limited to silanes which have an ethylenediamine unit.